Compared with the conventional infrared or visible light detectors or sensors, the high-energy UV-light detectors or sensors have many advantages, such as strong ability to anti-interference, reduced probability of false triggering or alarming events, etc. Thus UV-light detection and sensing technology are widely used in the flame and thermal sensor, missile tail flame detection, forest fire detection and explosion gas detection. Taking detection of gas explosion as an example, there is high-energy radiation with different spectrum releasing before the gas explosion. And there is abundant information in the radiated rays, such as the ultraviolet ray. Through the detection of high energy X-ray, we can predict the occurrence of disaster in advance and then reduce the loss of life and property. Due to the high energy of the UV light, the semiconductor devices with wide band gap must be used. The mentioned wide band gap semiconductors include gallium arsenide (GaAs), gallium nitride (GaN) and so on. However, the process of semiconductor devices with wide band gap semiconductor materials are complicated and high processing temperature is required, and it is not suitable for large-area manufacturing.
In recent years, many ultraviolet detectors integrated with oxide TFT were emerged. Due to the rapid development of the flat panel display technology, indium gallium zinc oxide (IGZO) TFT has recently become the research hotpots. The silicon TFT technology may be replaced by IGZO TFTs which is regarded as the mainstream of the next generation TFT. It is noteworthy that, when IGZO and other oxides are exposed to ultraviolet light, the electrical characteristics of the oxide TFT may be changed significantly. For example, the threshold voltage will be decreased, and the off-current will be increased by orders of magnitude. Therefore, the UV detector can be realized by taking advantage of optical and electrical characteristic of Oxide TFTs. In addition, the oxide TFT has many advantages, for example, the manufacturing process is relatively simple, and the processing temperature is low, and it is suitable for large area production. The function of oxide TFT UV detection may even be implemented in the display panel, thus system integration on the display panel (system on panel, SOP) can be realized. So the UV light intensity of environment can be read by the display panel, and even the profile of the ultraviolet-emitting objects can be demonstrated. Thus it is suitable for the early detection of light emission or explosion with strong sunlight or infrared background.
Up to now, there has not been a mature scheme of ultraviolet light sensing circuit based on oxide TFT. Especially in applications of the early warning of forest fire or gas explosion, the detection of ultraviolet signal and the transmission of detected ultraviolet signal are still serious problems that are in urgent to be solved.